The VOD plugin for Wordpress can encounter problems if you have installed other Wordpress plugins which are usually used for restricting access to your website, such as Members Only for example.

When curious problems occur, start by disabling (not "delete") one by one the other Wordpress plugins which could be problematic.

In the specific case where a video would indefinitely remain in a "conversion in progress" status, you can also simply click on "Synchronize" in the Wordpress VOD plugin settings and your video will be displayed correctly.